1. Field of the Invention
The present invention relates to a recording method used in a high density magnetic recording apparatus such as a digital recording video cassette recorder (digital VCR).
2. Description of the Prior Art
The digital VCR is currently being studied as a means for recording sounds and pictures by digital signals of 0 and 1 for the purpose of obtaining higher picture quality and higher sound quality. In particular, video signals contain a large amount of information, and to record such signals for a long time period, high density recording of information on a tape is indispensable. Two methods are presently adopted present for high density recording. A first method is to shorten a length necessary for recording one bit, i.e., enhancing a so-called line density. A second method is to narrow a track width.
To enhance the line density , hitherto, improvements in recording materials and signal processing have resulted in a line density of about 0.25 .mu.m for recording one bit. On the other hand, tracking width is said to be limited to around 10 .mu.m in a VCR due to the limitations in the mechanical precision in recording and reproducing, and in tracking control for obtaining a stable reproduced output. In an 8 mm VCR, a pilot signal is superposed and recorded in video signals and audio signals for the purpose of tracking control.
In the case of the digital VCR for recording video signals and audio signals as digital signals, a quantity of information to be recorded is very large as compared with that of an analog VCR. That is, high density recording is more necessary for the digital VCR than the analog VCR.
In the digital VCR, a recording signal band is much wider than in the analog VCR, and it is difficult to assign a frequency for pilot signals in a frequency band other than a signal to be recorded as in the case of the 8 mm VCR. It is thus necessary to assign a pilot signal frequency within the frequency band of the signal to be recorded. Also, to realize a narrow track width, it is necessary to raise a ratio of a amplification level of the pilot signal to a noise level of the pilot signal.
However, when the amplification level of the pilot signal is increased, an amplitude of a signal other than an original signal to be recorded is also increased, and the pilot signal results in a disturbance during reproducing, and an error rate in judging whether each bit is 1 or 0 becomes higher. Accordingly, if a signal other than a signal to be recorded is superposed as the pilot signal, an amplitude of the pilot signal cannot be increased. If the amplitude of the pilot signal cannot be increased, signal to noise ratio (S/N) of the pilot signal in a reproduced signal becomes poor, and the tracking precision is degraded. Therefore, in a system for superposing a signal other than the signal to be recorded as a pilot signal, it is difficult to realize a narrow track width.